No (good) reason at all! My generator is based on GitHub fork of bitaddress.org from about 2 weeks ago, so whatever bitaddress.org was using back then I'm still using now. I haven't folded in any recent developments (including BIP38 which I'm considering implementing.) I'll have to ask if pointbiz/bitaddress.org are using the older crypto for compatibility reasons or if it just needs refreshing.

I've also been thinking about building in some very human random input other than mouse movement... like an option to flip coins or throw dice or something...

I'm enormously grateful for any source code checking anyone wants to do, especially for a forthcoming live bootable CD I intend to distribute. (Someone generously ported my design to their own linux-based command line generator which uses an in-memory filesystem and PDF generation to circumvent issues with cached print files ending up on the hard drive, etc.)

Hi Charles,
Lecture looks *great* I skimmed it. Really glad to see a detailed straightforward explanation in such depth.

I've been experimenting with spraying the finished printouts with Krylon "Preserve It" before folding up. Stinky as hell, but I think it's going to make a difference as long as their marketing info is accurate:

• Digital photo and paper protectant more than doubles the life of documents and photos.
• Ideal for protecting digital photos, address labels, greeting cards, scrapbook materials, artwork and more
• Acid-free/Archival-safe

Jinx. I just did that -- literally -- 10 minutes ago.

See the bottom right of the notes/deposit area:

https://bitcoinpaperwallet.com/bitcoinpaperwallet/images/back-300dpi.jpg

- Canton

PS: If you haven't yet voted on your favorite open source bitcoin paper wallet design, hurry up, voting is ending soon!
https://tricider.com/en/brainstorming/poxx

For fun, maybe instead of QR codes, random dot stereograms Seriously though, I thought of doing bogus QR codes but I was afraid of usability issues for novices... maybe if there's a real obvious "NOT HERE" type mark. I'll think about this some more.

For what it's worth, I'm hoping and assuming that this has been the plan all along. I think the contest was a good motivation to get us hunkered down in front of our computers working on original designs. However, when the contest is over I don't imagine the point is to send the "winning" design to the printers -- rather I assume since this is an open and collaborative project that Aantonop will consider integrating elements from any of the designs (winning or not) to make something truly spectacular.

Everyone's been very generous with sharing ideas up until this point, I can't imagine why the collaboration would stop now.

With any combination of zoom/shift settings, did you manage to get the calibration page to print out perfectly *centered* (horizontally centered, that is?) That's the factor that influences how accurately the front/back line up. For zoom 3 / shift 7, what browser / OS were you using?

If anyone reading this thread is scratching their heads, this is what we're talking about:



So far I've had the best success with Safari, pretty good with Firefox & IE, possibly some problems with Chrome.


Not yet. I'll think about that some, like a "master zoom" function. However the resulting wallets wouldn't size properly for the tamper-evident tape I sourced -- so you'd be obligated to use regular tape.

Definitely still works with regular tape, especially if you're mostly concerned about casual tampering (wallet on the table) as opposed to dedicated fooling around with liquid solvents and heat guns.

To this end:

#1: Today I soft-launched https://bitcoinpaperwallet.com which not only provides the wallet generator (in-browser two-sided printing) but also features security tips, and allows you to purchase custom holograms using bitcoin. Wallet generator is open-source and can run entirely offline as it's based on bitaddress.org.

#2: Somewhat unrelated, but I entered a variation of my design for a *non-folding* project organized on bitcointalk.org. These paper wallets will be professionally printed (any you'll only home-print the keys/QR codes.) Have a look and vote for whichever design appeals most to you: https://tricider.com/en/brainstorming/poxx

Done! I don't think the margins are ideal in the template (important content unnecessarily close to the paper edge) -- and I think it's a mistake to omit the public key from the backup stub -- but I've submitted a revised design that strictly conforms to the template.

https://tricider.com/en/display/104330?wicket:pageMapName=wicket-4

Thanks, and again thanks for your extremely useful feedback.

For anyone who doesn't quite see how the new design addresses yellowcoin's "pull out the fold with stickytape" hack, here's how the new design folds up In Real Life



Now the two strips of tamper-evident tape stick to all 3 panels of the fold, preventing it from being snuck out.

Okay, I finally posted mine to tricider for voting, and for the first time, included the reverse design as well.



http://tricider.com/brainstorming/poxx -- voting begins tomorrow I think?

Hmm, I hope this is just a blurring/resolution issue from taking a screenshot and then shrinking the size and applying JPG. I'm using the same code and QR generator as bitaddress.org -- the only fundamental difference is the web interface, CSS/HTML and the background art.

Here's a non-downscaled sample. Would you see if the sample below reads correctly 10/10 for you? The QR codes when printed are quite sharp. Significantly sharper than this JPG.

I worked on about 5 or 6 variations last night before I hit on this one which isn't significantly more difficult to cut out with scissors. In my own tests, this new shape overcomes this exploit while still using the original design that calls for two strips of 2" x .625" tamper-evident tape. (When you fold this new design up, the tape now sticks to all three "panels" in the folded area so the innermost panel can't be snuck out.)

Thanks again yellowcoin for the excellent experiment.



PS: Yes, those are live keys, but there's nothing stored in them this time. Yet.

How's this for an updated reverse?

A million percent agreed. Here's the current back of the wallet, though I wonder if the point should be amplified...




And here's the related bit of instructions as they'll appear on the web. Note the tip in the middle. Especially that typo. Oops.



The link to "lose your balance forever" goes to this excellent thread:
http://www.reddit.com/r/Bitcoin/comments/1c9xr7/psa_using_paper_wallets_understanding_change/

I welcome any edits/ideas/additions to making this hugely important point as clear as possible.

THAT IS FRIGGING AWESOME. I didn't think it was possible reading your post, but then I tried it myself on a test wallet and was able to reveal the inner flap without disturbing the tape. That's a superb low-tech work-around, nice job.

I could add a third sticker requirement to cover the open fold - could even be a nice circular hologram of a BTC or something. Or, I could change the design so it includes an extra cut in the middle like so:



This way the tape holds down the innermost flap as well.

I can't quite decide whether it's better to have more stickers plastered on the thing, or require that users make an additional (farily deft) set of cuts. Opinions?


Good idea. I'll have to experiment with dry heat (if Niko hasn't already) to see if these tamper-evident stickers are susceptible.

Thanks for the excellent feedback. Just sent you a beers-worth of BTC to your address.
https://blockchain.info/address/15kFAbgWsSM28N7x5ZbWAehABkGnp9dPPT

Well I found out a couple hours after Niko first noticed the balance was missing. I've just been too embarrassed to fess up to what happened. Here's the skinny:

Back when I generated Niko's test wallet I was still using a photoshop template to make these wallets. (Now I'm using a fork of bitaddress.org / javascript.) The same day that I printed out his wallet, I also did some work in photoshop on a different (non-folding) bitcoin template for another project on bitcointalk.org. I used my photoshop template as a starting point (which still had Niko's codes on it) and I accidentally included the QR code from Niko's test wallet in a couple of design templates over here:

https://bitcointalk.org/index.php?topic=155847.100

Someone apparently tried out the codes, realized there was a balance, and swiped the wallet. That person was kind enough to contact me anonymously and let me know that s/he had swiped the bounty. If Niko wins the bet I'll just have to send him his BTC the "old fashioned" way.

tl/dr: I screwed up and posted an image containing the private key QR code to bitcointalk.org.

Aantonop,

Any tests/results yet to see whether or not the scratch-off seal on heavy stock is susceptible to "candling", or if they help with waterproofing? I'm especially curious to know if these stickers are an effective light-guard.

Exactly what niko suspected. If you poke through this thread you'll see that he and I have a friendly wager to see if the wallet can be "candled" without tampering with the tape. I hope he finds some weaknesses I can improve on! (I'm confident that there's *some* way to make a secure folding wallet, even if I didn't get it right this time.)

Hey everyone, I did something REALLLLLY foolish:

You know those mockups I posted of my design in this thread? The QR codes contained a live public address AND private key with a small balance (.026 BTC) -- part of an unrelated competition I was running. Dumb dumb dumb...

On April 11 the wallet was swiped before the competition even began:
https://blockchain.info/address/1LMKzdqhQ4LhHy5GGhT8BcG3HHpBTqAqbt

If you're reading this thread and you swiped the wallet by cleverly reading the QR code off of the mockups I posted to this thread, would you please please let me know? You can ping me at canton@gmail.com. This would be much more reassuring than the alternative explanation I have which is that my computer or internet connection was hacked.

In fact, if you can prove you were the person who emptied the wallet, I'll gladly send you *another* .026 BTC for your trouble.

Thanks,
- Your friendly village idiot